Organic electroluminescent display device having electroluminescent transistors and methods of manufacturing the device

ABSTRACT

An electroluminescent display device is disclosed. The device includes electroluminescent transistors which function as both signal switches and as electroluminescent light sources for the display pixels.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No.10-2004-0094179, filed on Nov. 17, 2004, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescent (EL)device and a method of manufacturing the same, and more particularly, toan EL device with low manufacturing costs and improved yield due tosimplified structure and use of an organic light emitting transistor(OLET) and a method of manufacturing the same.

2. Description of the Related Technology

Flat display devices such as liquid crystal devices, EL devices, or inEL devices are classified into passive matrix (PM) and active matrix(AM) according to their driving methods. In passive matrix flat displaydevices, anodes and cathodes are arranged in columns and rows,respectively. A row driving circuit supplies a scanning signal to one ofthe cathodes to select only one row and a column driving circuitsupplies a data signal to each pixel of the selected row. Because thereare no transistor-capacitor circuits for the pixels, the image is notstored between refresh cycles and the image is less bright and sharpthan an active matrix display.

On the other hand, an active matrix flat display device controls asignal input to each pixel using thin film transistors and is suitablefor displaying a plurality of images. Accordingly, active matrix displaydevices are widely used as display devices for displaying a movingpicture.

The thin film transistors of active matrix flat display devices eachhave source and drain regions in which impurities are heavily doped, asemiconductor layer having a channel region between the source and drainregions, a gate electrode which is insulated from the semiconductorlayer and is located above the channel region, and source and drainelectrodes contacting the source and drain regions, respectively.

The semiconductor layer is often composed of amorphous silicon or polysilicon. Amorphous silicon can be deposited at low temperature, but haselectric characteristics that is deteriorated and thus is unreliable andcan not easily realize a large-area flat display device. Accordingly,poly silicon is widely used. Since poly silicon has high currentmobility of several tens through several hundreds of cm²/V·s, excellenthigh-frequency operation characteristics, and a low leakage current, itis suitable for a high-precision and large-area flat display device.

However, if the semiconductor layer is made of poly silicon, a processfor crystallizing amorphous silicon is required. The crystallizingprocess must be generally performed at a high temperature of 300° C. Inthis case, a substrate composed of, for example, a plastic material forrealizing a flexible display device can not be used. Accordingly,research into an organic thin film transistor which does not require thecrystallizing process has increased.

Flat display devices require high operating speeds and uniform qualityin order to process a high quality moving picture. Particularly, in thecase of an EL device, a circuit having excellent characteristics must berealized in order to display the moving picture with high quality. Thatis, in an EL device, a driving element (transistor) is separatelyprovided to each pixel in addition to a switching element (transistor)for switching each pixel. Also, a plurality of thin film transistors mayfurther be included in various compensating circuits associated with thedisplay.

If the EL device has a display unit connected to the circuit having theabove-mentioned complicated structure, the manufacturing process thereofis complicated and, the yield thereof is decreased, thus resulting inincreased manufacturing costs.

SUMMARY OF CERTAIN INVENTIVE EMBODIMENTS

The present invention provides an EL device with low manufacturing costsand improved yield due to simplified structure and use of an organiclight emitting transistor (OLET) and a method of manufacturing the same.

One embodiment includes an organic electroluminescent device including afirst organic light emitting transistor including a first sourceelectrode, a first drain electrode, a first intermediate layer includingat least an emission layer formed between the first source electrode andthe first drain electrode, and a first gate electrode insulated from thefirst source electrode, the first drain electrode, and the firstintermediate layer, the first gate electrode surrounding the firstintermediate layer. The embodiment also includes a second organic lightemitting transistor including a second source electrode, a second drainelectrode, a second intermediate layer including at least an emissionlayer formed between the second source electrode and the second drainelectrode, and a second gate electrode insulated from the second sourceelectrode, the second drain electrode, and the second intermediatelayer, the second gate electrode surrounding the second intermediatelayer and being connected to the first drain electrode.

Another embodiment includes a method of manufacturing an organicelectroluminescent device. The method includes forming a first sourceelectrode and a second source electrode over a substrate, forming acapacitor insulating layer over the substrate to cover at least thefirst source electrode and the second source electrode, forming firstand second gate electrodes over the capacitor insulating layer eachhaving a donut shape, where the location of the first and second gateelectrodes correspond to the locations of the first source electrode andthe second source electrode, respectively. The method also includesforming a planarization film over the substrate to cover at least thefirst gate electrode and the second gate electrode, forming a mask ofhigh molecular weight material over the planarization film, formingthrough-holes in the mask, the planarization film, and the capacitorinsulating layer to expose upper surfaces of the first source electrodeand the second source electrode and side surfaces of the planarizationfilm, the first gate electrode, the second gate electrode, and thecapacitor insulating layer, forming gate insulating films to cover theside surfaces of the planarization film, the first gate electrode, thesecond gate electrode, and the capacitor insulating layer exposed by thethrough-holes, forming an intermediate layer including at least anemission layer in each of the through-holes, removing the mask, forminga contact hole in the planarization film to expose a portion of thesecond gate electrode, and forming over the intermediate layers a firstdrain electrode in a location corresponding to the location of the firstsource electrode and a second drain electrode in a locationcorresponding to location of the second source electrode, where thefirst drain electrode is connected to the second gate electrode throughthe contact hole.

Another embodiment includes a method of manufacturing an organicelectroluminescent device. The method includes forming a first sourceelectrode and a second source electrode over a substrate, forming acapacitor insulating layer over the substrate to cover at least thefirst source electrode and the second source electrode, forming firstand second gate electrodes over the capacitor insulating layer eachhaving a donut shape, where the location of the first and second gateelectrodes correspond to the locations of the first source electrode andthe second source electrode, respectively, forming a planarization filmover the substrate to cover at least the first gate electrode and thesecond gate electrode, forming through-holes in the planarization filmand the capacitor insulating layer to expose upper surfaces of the firstsource electrode and the second source electrode and side surfaces ofthe planarization film the first gate electrode, the second gateelectrode, and the capacitor insulating layer. The method also includesforming gate insulating films to cover the side surfaces of theplanarization film, the first gate electrode, the second gate electrode,and the capacitor insulating layer exposed by the through-holes, formingan intermediate layer including at least an emission layer in each ofthe through-holes, forming a contact hole in the planarization film toexpose a portion of the second gate electrode, and forming over theintermediate layers a first drain electrode in a location correspondingto the location of the first source electrode and a second drainelectrode in a location corresponding to the location of the secondsource electrode, where the first drain electrode is connected to thesecond gate electrode through the contact hole.

Another embodiment includes an organic electroluminescent deviceincluding a first organic electroluminescent transistor, and a secondorganic electroluminescent transistor, where the drain of the firstorganic electroluminescent transistor is connected to the gate of thesecond organic electroluminescent transistor.

Another embodiment includes an organic electroluminescent deviceincluding a first organic electroluminescent transistor configured toselectively emit light according to a first signal, and a second organicelectroluminescent transistor configured to selectively connect thefirst organic electroluminescent transistor to the first signal, wherethe connectivity is based on a second signal.

Another embodiment includes a method of manufacturing anelectroluminescent device, the method including forming a first organicelectroluminescent transistor, configuring the first organicelectroluminescent transistor to selectively emit light according to afirst signal, forming a second organic electroluminescent transistor,and configuring the second organic electroluminescent transistor toselectively connect the first organic electroluminescent transistor tothe first signal, where the connectivity is based on a second signal.

Another embodiment includes a method of using an electroluminescentdevice. The method includes driving a data signal to a first organicelectroluminescent transistor, and driving a control signal to the firstorganic electroluminescent transistor, where the state of a firstorganic electroluminescent transistor changes so as to connect the datasignal to a second organic electroluminescent transistor, and where theluminescence of the second organic electroluminescent transistorsubstantially changes.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of certain inventive aspectsare discussed with further detailed exemplary embodiments with referenceto the attached drawings in which:

FIG. 1 is a cross-sectional view of an EL device according to anembodiment;

FIG. 2 is a circuit diagram of a display device using the EL deviceshown in FIG. 1;

FIG. 3 is a circuit diagram of a portion “A” shown in FIG. 2;

FIG. 4 is a perspective view of an organic light emitting transistorincluded in the EL device shown in FIG. 1;

FIG. 5 is a cross-sectional view of an EL device according to anotherembodiment;

FIG. 6 is a perspective view of a portion of an organic light emittingtransistor included in the EL device shown in FIG. 5;

FIGS. 7 through 13 are cross-sectional views schematically illustratinga method of manufacturing an EL device according to an embodiment; and

FIGS. 14 through 19 are cross-sectional views schematically illustratinga method of manufacturing an EL device according to another embodiment.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

Exemplary embodiments will now be described more fully with reference tothe accompanying drawings.

FIG. 1 is a cross-sectional view of an organic electroluminescent ELdevice according to an embodiment, FIG. 2 is a circuit diagram of adisplay device using the EL device shown in FIG. 1, FIG. 3 is a circuitdiagram of a portion “A” shown in FIG. 2, and FIG. 4 is a perspectiveview of an organic light emitting transistor included in the EL deviceshown in FIG. 1.

Hereinafter, the structure of the EL device of the present embodimentwill be described with reference to the drawings.

A first organic light emitting transistor 110 and a second organic lightemitting transistor 120 are electrically connected to each other on acommon substrate 100. The substrate may, for example, be formed ofplastic or glass. The first organic light emitting transistor 110includes a first source electrode 111, a first drain electrode 112, afirst intermediate layer 113, and a first gate electrode 114. The firstsource electrode 111 and the first drain electrode 112 are on oppositesides of the intermediate layer 113. The first intermediate layer 113 isdisposed between the first source electrode 111 and the first drainelectrode 112 and has at least an emission layer 1133. The first gateelectrode 114 is insulated from the first source electrode 111, thefirst drain electrode 112, and the first intermediate layer 113 andsurrounds the first intermediate layer 113.

The second organic light emitting transistor 120 includes a secondsource electrode 121, a second drain electrode 122, a secondintermediate layer 123, and a second gate electrode 124. The secondsource electrode 121 and the second drain electrode 122 are opposite toeach other. The second intermediate layer 123 is disposed between thesecond source electrode 121 and the second drain electrode 122 and hasat least an emission layer 1233. The second gate electrode 124 isinsulated from the second source electrode 121, the second drainelectrode 122, and the second intermediate layer 123 and surrounds thesecond intermediate layer 123. The first drain electrode 112 isconnected to the second gate electrode 124.

Referring to FIG. 1, the first source electrode 111 and the secondsource electrode 121 may be formed in the same layer, the first drainelectrode 112 and the second drain electrode 122 may be formed in thesame layer, and the first gate electrode 114 and the second gateelectrode 124 may be formed in the same layer.

The source electrodes 111 and 121 may comprise transparent materialssuch as ITO, IZO, ZnO or In₂O₃. If the source electrodes 111 and 121 areused as reflective electrodes, they may comprise reflective films suchas Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr or a combination thereof withtransparent materials such as ITO, IZO, ZnO or In₂O₃ formed thereon.

The drain electrodes 112 and 122 may include a thin metal layer made ofmaterial having a small work function, such as Li, Ca, LiF/Ca, LiF/AI,Al, Ag, or Mg or a combination thereof, deposited toward theintermediate layers 113 and 123 and Other electrode layers or buselectrode lines made of a material for forming a transparent electrodesuch as ITO, IZO, ZnO or In₂O₃ may be formed on the metal. When thedrain electrodes 112 and 122 are used as reflective electrodes, they maybe made of a metal such as Li, Ca, LiF/Ca, LiF/Al, Al, Ag, or Mg or acombination thereof. The electrodes are not limited to these materials,and the source electrodes 111 and 121 and the drain electrodes 112 and122 may also be made of organic materials such as a conductive polymer.

A capacitor 130 may further be included in the EL device. The capacitor130 includes a first capacitor electrode 131 and a second capacitorelectrode 132. The first capacitor electrode 131 is connected to thesecond gate electrode 124, and the second capacitor electrode 132 isconnected to the second source electrode 121. The first capacitorelectrode 131 may be integrally formed with the second gate electrode124 and the second capacitor electrode 132 may be integrally formed withthe second source electrode 121.

A capacitor insulating layer 140 is formed between the first capacitorelectrode 131 and the second capacitor electrode 132. Accordingly, thecapacitor insulating layer 140 is formed between a layer including thefirst gate electrode 114 and the second gate electrode 124 and a layerincluding the first source electrode 111 and the second source electrode121, referring to FIG. 1. The capacitor insulating layer 140 may be madeof an inorganic material or an organic material.

A planarization film 150 may further be formed on the first gateelectrode 114 and the second gate electrode 124, which are formed on thecapacitor insulating layer 140. The first drain electrode 112 and thesecond drain electrode 122 may be formed on the planarization film 150.In order to connect the first drain electrode 112 with the second gateelectrode 124, a contact hole 150 a is formed in the planarization film150. That is, the first drain electrode 112 is connected to the secondgate electrode 124 through the contact hole 150 a.

The first intermediate layer 113 may have various shapes, for example,it may have a cylindrical shape of which a central axis extends from thefirst source electrode 111 to the first drain electrode 112. Also, thesecond intermediate layer 123 may be formed in various shapes, forexample, it may have a cylindrical shape of which a central axis extendsfrom the second source electrode 121 to the second drain electrode 122.The intermediate layers 113 and 123 may also have another shape such asa parallelepiped shape or an irregular shape. In the embodimentsdescribed below, it is assumed for convenience that the intermediatelayer 123 has a cylindrical shape.

As mentioned above, the first gate electrode 114 is insulated from thefirst source electrode 111, the first drain electrode 112, and the firstintermediate layer 113, and has a donut shape surrounding the firstintermediate layer 113. Accordingly, in order to insulate the first gateelectrode 114 from the first source electrode 111, the first drainelectrode 112, and the first intermediate layer 113, a gate insulatingfilm 115 may further be formed between the first intermediate layer 113and the first gate electrode 114. Similarly, a gate insulating film 125may further be formed between the second intermediate layer 123 and thesecond gate electrode 124.

If the first intermediate layer 113 and the second intermediate layer123 have the cylindrical shapes as mentioned above, the gate insulatingfilms 115 and 125 have donut shapes so as to surround the side surfacesof the first intermediate layer 113 and the second intermediate layer123.

The intermediate layers 113 and 123 may be made of low molecular weightmaterials. In FIG. 1, the intermediate layers 113 and 123 respectivelyinclude hole injection layers (HIL) 1131 and 1231, hole transport layers(HTL) 1132 and 1232, emission layers (EML) 1133 and 1233, hole blockinglayers (HBL) 1134 and 1234, and electron transport layers (ETL) 1135 and1235 formed between the source electrodes 111 and 121 and the drainelectrodes 112 and 122. The organic material of the intermediate layer113 or 123 may include copper phthalocyanine (CuPc),N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB),tris-8-hydroxyquinoline aluminum (Alq₃), or the like. The intermediatelayers 113 and 123 may have the other structures. The same is true inthe subsequently-described embodiments.

Referring to FIG. 1, the intermediate layers 113 and 123 include atleast the hole transport layers 1132 and 1232, respectively. The firstgate electrode 114 may surround the hole transport 1132 of the firstintermediate layer 113 and the second gate electrode 124 may surroundthe hole transport layer 1232 of the second intermediate layer 123. Inthis case, the second gate electrode 124 may completely or partiallysurround the hole transport layer 1232. The same is true in thesubsequently-described embodiments. In this case, the hole transportlayers 1132 and 1232 function as the semiconductor layers.Alternatively, the intermediate layers 113 and 123 may include at leastthe hole injection layers 1131 and 1231, the first gate electrode 114may surround the hole injection layer 1131 of the first intermediatelayer 113, and the second gate electrode 124 may surround the holeinjection layer 1231 of the second intermediate layer 123.Alternatively, the intermediate layers 113 and 123 may include at leastthe hole blocking layers 1134 and 1234, the first gate electrode 114 maysurround the hole blocking layer 1134 of the first intermediate layer113, and the second gate electrode 124 may surround the hole blockinglayer 1234 of the second intermediate layer 123. Alternatively, theintermediate layers 113 and 123 may include at least the electrontransport layers 1135 and 1235, the first gate electrode 114 maysurround the electron transport layer 1135 of the first intermediatelayer 113, and the second gate electrode 124 may surround the electrontransport layer 1235 of the second intermediate layer 123. The locationof the intermediate layer or the location of the gate electrode may bechanged. The same is true in the subsequently-described embodiments.

The operating principle of the EL device having the above-mentionedstructure will now be described with reference to FIG. 3.

If a scan signal is applied by a driving circuit to the first gateelectrode 114 of the first organic light emitting transistor 110connected to a first wire 170, a conductive channel is formed in thehole transport layer 1132 of the intermediate layer 113 surrounded bythe first gate electrode 114. In this case, if a data signal is appliedto the first source electrode 111 of the first organic light emittingtransistor 110 through a second wire 180, the data signal is applied tothe capacitor 130 and the second gate electrode 124 of the secondorganic light emitting transistor 120 through the first drain electrode112 of the first organic light emitting transistor 110. Thus, aconductive channel is formed in the hole transport layer 1232 of theintermediate layer 123 of the second organic light emitting transistor120. An electric signal from a third wire 190 is adjusted to adjust theamount of light generated in the intermediate layer 123 including theemission layer 1233 of the second organic light emitting transistor 120.Thus, the first organic light emitting transistor 110 acts as atransistor to connect the data signal placed on the second wire 180 tothe second organic light emitting transistor 120, which acts as anelectroluminescent display element.

In the above-mentioned driving method, the first wire 170 is a scanline, the second wire 180 is a data line, and the third wire 190 is apower supply line (Vdd line).

As mentioned above, the EL device can be realized without using aseparate thin film transistor, that is, only using the organic lightemitting transistor, and thus the structure of the EL device and themanufacturing process thereof can be simplified. Accordingly, themanufacturing costs can be reduced and the yield can be improved.

FIG. 5 is a cross-sectional view of an EL device according to anotherembodiment, and FIG. 6 is a perspective view of a portion of an organiclight emitting transistor included in the EL device shown in FIG. 5.

The present embodiment is different from the above-mentioned embodimentin the structure of intermediate layers 213 and 223.

While the intermediate layers 113 and 123 included in the EL devices 110and 120 are made of the low molecular weight organic materials in theabove-mentioned embodiments, the intermediate layers 213 and 223included in the EL devices 210 and 220 are made of high molecular weightorganic materials in the present embodiment. In the present embodiment,the intermediate layers 213 and 223 may include hole transport layers2132 and 2232 and emission layers 2133 and 2233. The hole transportlayer may be made of PEDOT and the emission layer may be made of a highmolecular weight organic material such as poly-phenylenevinylene orpolyfluorene. Other layers may further be included in the intermediatelayer 213 and 223 and other materials may be used.

In some embodiments, the EL device can be realized without using aseparate thin film transistor, that is, only using the organic lightemitting transistor, and thus the structure of the EL device and themanufacturing process thereof can be simplified. Accordingly, themanufacturing costs can be reduced and the yield can be improved.

FIGS. 7 through 13 are cross-sectional views schematically illustratingan exemplary method of manufacturing an EL device according to anembodiment. Modifications to the example may be made resulting inalternate embodiments of the method which would generate variousembodiments of the EL device.

Referring to FIG. 7, a first source electrode 111 and a second sourceelectrode 121 are formed on a substrate 100 which is made of glass orplastic. Predetermined patterning is then performed usingphotolithography. Next, a capacitor insulating layer 140 is formed onthe entire surface of the substrate 100 so as to cover the first sourceelectrode 111 and the second source electrode 121. The capacitorinsulating layer 140 may made of an organic material or inorganicmaterial. A first gate electrode 114 and a second gate electrode 124having donut shapes are formed on the capacitor insulating layer 140above the first source electrode 111 and the second source electrode121, respectively. The deposition is performed using a fine metal maskand predetermined patterning is performed using photolithography. Afterforming the first gate electrode 114 and the second gate electrode 124,a planarization film 150 is formed on the entire surface of thesubstrate 100 so as to cover the first gate electrode 114 and the secondgate electrode 124, and a mask of high molecular weight material 160 isformed on the planarization film 150.

Subsequently, referring to FIG. 8, through-holes 150 b and 150 c areformed in the mask of high molecular weight material 160, theplanarization film 150, and the capacitor insulating layer 140 to exposethe upper surfaces of the first source electrode 111 and the secondsource electrode 121 and the side surfaces of the first gate electrode114 and the second gate electrode 124. In order to form thethrough-holes 150 b and 150 c, laser ablation technology (LAT) may beused.

Next, referring to FIG. 9, gate insulating films 115 and 125 are formedto cover the side surfaces of the planarization film 150, the first gateelectrode 114, the second gate electrode 124, and the capacitorinsulating layer 140 exposed by the through-holes 150 b and 150 c. Thegate insulating films 115 and 125 can be formed by oxidizing thesurfaces of the planarization film 150, the first gate electrode 114,the second gate electrode 124, and the capacitor insulating layer 140exposed by the through-holes 150 b and 150 c. In this case, the gateinsulating films 115 and 125 can be formed, for example, by performingan O₂ plasma treatment or H₂O₂ treatment. Other methods may also beused.

Next, referring to FIG. 10, a low molecular weight material is depositedusing the mask of high molecular weight material 160 to formintermediate layers 113 and 123 including at least emission layers inthe through-holes 150 b and 150 c, respectively. The shapes and kinds ofthe intermediate layers are not limited to those shown in FIGS. 11through 13.

Referring to FIG. 11, the mask of high molecular weight material 160 isremoved and, referring to FIG. 12, a contact hole 150 a is formed in theplanarization film 150 to expose a portion of the second gate electrode124. Finally, a first drain electrode 112 corresponding to the firstsource electrode 111 and a second drain electrode 122 corresponding tothe second source electrode 121 are formed on the intermediate layer 113and 123 so that the first drain electrode 112 is connected to the gateelectrode 124 through the contact hole 150 a. Accordingly, the EL deviceis completed, referring to FIG. 13.

By the above-mentioned process, the EL device can be realized withoutusing a separate thin film transistor, that is, only using the organiclight emitting transistor, and thus the structure of the EL device andthe manufacturing process thereof can be simplified. Accordingly, themanufacturing costs can be reduced and the yield can be improved.

FIGS. 14 through 19 are cross-sectional views schematically illustratinganother method of manufacturing an EL device according to anotherembodiment.

Referring to FIG. 14, a first source electrode 211 and a second sourceelectrode 221 are formed on a substrate 200 which is made of glass orplastic. Predetermined patterning is then performed usingphotolithography. Next, a capacitor insulating layer 240 is formed onthe entire surface of the substrate 200 so as to cover the first sourceelectrode 211 and the second source electrode 221. The capacitorinsulating layer 240 may be made of an organic material or an inorganicmaterial. A first gate electrode 214 and a second gate electrode 224having donut shapes are formed on the capacitor insulating layer 240above the first source electrode 211 and the second source electrode221, respectively. The deposition is performed using a fine metal maskand predetermined patterning is performed using photolithography. Afterforming the first gate electrode 214 and the second gate electrode 224,a planarization film 250 is formed on the entire surface of thesubstrate 200 so as to cover the first gate electrode 214 and the secondgate electrode 224.

Subsequently, referring to FIG. 15, through-holes 250 b and 250 c areformed in the planarization film 250 and the capacitor insulating layer240 to expose the upper surfaces of the first source electrode 211 andthe second source electrode 221 and the side surfaces of the first gateelectrode 214 and the second gate electrode 224. In order to form thethrough-holes 250 b and 250 c, laser ablation technology (LAT) may beused.

Next, referring to FIG. 16, gate insulating films 215 and 225 are formedso as to cover the side surfaces of the planarization film 250, thefirst gate electrode 214, the second gate electrode 224, and thecapacitor insulating layer 240 exposed by the through-holes 250 b and250 c. The gate insulating films 215 and 225 can be formed by oxidizingthe surfaces of the planarization film 250, the first gate electrode214, the second gate electrode 224, and the capacitor insulating layer240 exposed by the through-holes 250 b and 250 c. In this case, the gateinsulating films 215 and 225 can be formed by performing an O₂ plasmatreatment or H₂O₂ treatment, but other methods may be also used.

Next, referring to FIG. 17, a high molecular weight material isdeposited using an inkjet printing method to form intermediate layers213 and 223 including at least emission layers in the through-holes 250b and 250 c, respectively. The shapes and kinds of the intermediatelayers are not limited to those shown in FIGS. 17 through 19.

Referring to FIG. 18, a contact hole 250 a is formed in theplanarization film 250 such that a portion of the second gate electrode224 is exposed. Finally, a first drain electrode 212 corresponding tothe first source electrode 211 and a second drain electrode 222corresponding to the second source 221 are formed on the intermediatelayer 213 and 223 so that and the first drain electrode 212 is connectedto the second gate electrode 224 through the contact hole 250 a.Accordingly, the EL device is completed, referring to FIG. 19.

By the above-mentioned process, the EL device can be realized withoutusing a separate thin film transistor, that is, only using the organiclight emitting transistor, and thus the structure of the EL device andthe manufacturing process thereof can be simplified. Accordingly, themanufacturing costs can be reduced and the yield can be improved.

While the above description has pointed out novel features of theinvention as applied to various embodiments, the skilled person willunderstand that various omissions, substitutions, and changes in theform and details of the device or process illustrated may be madewithout departing from the scope of the invention. Therefore, the scopeof the invention is defined by the appended claims rather than by theforegoing description. All variations coming within the meaning andrange of equivalency of the claims are embraced within their scope.

1. An organic electroluminescent device comprising: a first organiclight emitting transistor comprising: a substrate; a first sourceelectrode; a first drain electrode facing the first source electrode; afirst intermediate layer comprising at least an emission layer formedbetween the first source electrode and the first drain electrode; and afirst gate electrode insulated from the first source electrode, thefirst drain electrode, and the first intermediate layer, the first gateelectrode surrounding the first intermediate layer, and wherein thefirst gate electrode, the first source electrode, and the first drainelectrode are positioned such that either: A) the first gate electrodeis nearer the substrate than the first source electrode and the firstdrain electrode is nearer the substrate than the first gate electrode,or B) the first gate electrode is farther from the substrate than thefirst source electrode and the first drain electrode is farther from thesubstrate than the first gate electrode; a second organic light emittingtransistor comprising: a second source electrode; a second drainelectrode facing the second source electrode; a second intermediatelayer comprising at least an emission layer formed between the secondsource electrode and the second drain electrode; and a second gateelectrode insulated from the second source electrode, the second drainelectrode, and the second intermediate layer, the second gate electrodesurrounding the second intermediate layer and being connected to thefirst drain electrode, and wherein the second gate electrode, the secondsource electrode, and the second drain electrode are positioned suchthat either: A) the second gate electrode is nearer the substrate thanthe second source electrode and the second drain electrode is nearer thesubstrate than the second gate electrode, or B) the second gateelectrode is farther from the substrate than the second source electrodeand the second drain electrode is farther from the substrate than thesecond gate electrode.
 2. The device according to claim 1, wherein thefirst source electrode and the second source electrode are substantiallyin a same first plane, the first drain electrode and the second drainelectrode are substantially in a same second plane, and the first gateelectrode and the second gate electrode are substantially in a samethird plane.
 3. The device according to claim 1, further comprising acapacitor comprising a first capacitor electrode connected to the secondgate electrode and a second capacitor electrode connected to the secondsource electrode.
 4. The device according to claim 3, wherein the firstcapacitor electrode is integrally formed with the second gate electrode.5. The device according to claim 3, wherein the second capacitorelectrode is integrally formed with the second source electrode.
 6. Thedevice according to claim 3, further comprising a capacitor insulatinglayer formed between a first plane comprising the first gate electrodeand the second gate electrode and a second plane comprising the firstsource electrode and the second source electrode.
 7. The deviceaccording to claim 6, wherein the capacitor insulating layer comprisesan organic material or an inorganic material.
 8. The device according toclaim 1, further comprising a planarization film formed over the firstgate electrode and the second gate electrode.
 9. The device according toclaim 8, wherein the first drain electrode and the second drainelectrode are formed over the planarization film.
 10. The deviceaccording to claim 8, wherein a contact hole is formed in theplanarization film, and the first drain electrode and the second gateelectrode are connected to each other through the contact hole.
 11. Thedevice according to claim 1, wherein the first intermediate layer has asubstantially cylindrical shape with a central axis extending from thefirst source electrode to the first drain electrode, and the secondintermediate layer has a substantially cylindrical shape with a centralaxis extending from the second source electrode to the second drainelectrode.
 12. The device according to claim 1, further comprising gateinsulating films which are formed between the first intermediate layerand the first gate electrode and between the second intermediate layerand the second gate electrode, respectively.
 13. The device according toclaim 12, wherein the first intermediate layer has a substantiallycylindrical shape with a central axis extending from the first sourceelectrode to the first drain electrode, and the second intermediatelayer has a substantially cylindrical shape with a central axisextending from the second source electrode to the second drainelectrode.
 14. The device according to claim 13, wherein the gateinsulating films surround the side surfaces of the first intermediatelayer and the second intermediate layer, respectively.
 15. The deviceaccording to claim 1, wherein the intermediate layers are made of a lowmolecular weight organic material or a high molecular weight organicmaterial.
 16. The device according to claim 15, wherein each of theintermediate layers comprise at least a hole injection layer, the firstgate electrode surrounds the hole injection layer of the firstintermediate layer, and the second gate electrode surrounds the holeinjection layer of the second intermediate layer.
 17. The deviceaccording to claim 15, wherein each of the intermediate layers compriseat least a hole transport layer, the first gate electrode surrounds thehole transport layer of the first intermediate layer, and the secondgate electrode surrounds the hole transport layer of the secondintermediate layer.
 18. The device according to claim 15, wherein eachof the intermediate layers comprise at least a hole blocking layer, thefirst gate electrode surrounds the hole blocking layer of the firstintermediate layer, and the second gate electrode surrounds the holeblocking layer of the second intermediate layer.
 19. The deviceaccording to claim 15, wherein each of the intermediate layers compriseat least an electron transport layer, the first gate electrode surroundsthe electron transport layer of the first intermediate layer, and thesecond gate electrode surrounds the electron transport layer of thesecond intermediate layer.